If by invention we mean actual technological advances — as opposed to ideas, theories and concepts — then there have been some good ones. One thinks of the printing press and the clock, for example. It is too early to say for sure but my choice for the most important invention of the past 2000 years would be the invention of the set of agricultural techniques known collectively as "The Green Revolution". This invention began in the 1960's and continues into the nineties, indeed, it is now being extended into something that may well come to be called "The Green-Blue Revolution", which would extend new agricultural techniques to the oceans.
The most important invention of all time is the Neolithic Revolution. With the Neolithic Revolution, humanity found ways to grow crops systematically, and thus overcame both the instability and the fragility of life itself that went with hunter-gatherer ways of survival. Hunter-gatherers could neither stay in one place long enough to develop a stable civilization, nor could they count on being able to survive periods of drought and other forms of natural catastrophe. With the Neolithic revolution, both of these problems were solved, and civilization became a real possibility.
However the Neolithic Revolution brought problems of its own. In particular, the Malthusian problem, because the growth of population was constantly threatening to outrun the growth of food supply. For the foreseeable future, at least, this problem has been solved by the Green Revolution. The food supply has vastly outrun the increase in population. At this time, if you read that there is a famine going on in some part of Africa or Asia, you know that it is deliberately politically created. There is no international shortage of food. There is plenty of food to go around, and because of the Green Revolution, there will be food to go around for the foreseeable future.